Re: surely....
The query part of this has a left outer join, so it includes all records from tblThis and just the matching records from tblThat.
Where there is no match, the query returns a null.
It therefore selects the records which are NOT IN tblThat.
The top line deletes these records from tblThis.
This is not standard SQL, however and wouldn't work in Oracle or MySQL.
The query part of this has a left outer join, so it includes all records from tblThis and just the matching records from tblThat.
Where there is no match, the query returns a null.
It therefore selects the records which are NOT IN tblThat.
The top line deletes these records from tblThis.
This is not standard SQL, however and wouldn't work in Oracle or MySQL.
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